The present invention relates to a so-called telemetering system, such as a system comprising a radiosonde (corresponding to a transmitter described later) having a variety of sensors for detecting atmospheric pressure, temperature and the like high up in the air, which is launched into the sky and transmits the detection data, a receiver for receiving the detection data on the ground and the like.
FIGS. 2(a) and 2(b) show one example of a configuration of a conventional telemetering system. That is, the telemetering system comprises a transmitter shown in FIG. 2(a) and a receiver shown in FIG. 2(b). In the transmitter shown in FIG. 2(a), a sensor 1 is a condition detecting element for detecting a condition (for example, temperature, humidity or pressure) at the position where the sensor is placed and providing a sensor output corresponding to the condition. An amplifier 2 is a circuit portion for amplifying the sensor output. An A/D converter 3 is a circuit portion for converting an analog signal of the sensor output, amplified by the amplifier 2, into the corresponding digital signal. A transmission circuit 4 is a circuit portion which modulates a predetermined carrier with the digital signal from the A/D converter 3, and then provides power-amplification and the like for the resultant modulated carrier to generate a transmission signal wave, and then outputs it to a transmitting antenna 5. The transmitting antenna 5 is a circuit portion for receiving the transmission signal wave and emitting the corresponding transmission wave into the air.
On the other hand, in the receiver shown in FIG. 2(b), a receiving antenna 6 is a circuit portion for receiving the transmission wave from the antenna 5 and generating an electrical signal corresponding to the transmission wave. A signal processor circuit 7 is a circuit portion for processing the electrical signal from the receiving antenna 6, such as amplifying and demodulating, to generate the received signal corresponding to the sensor output, or a received sensor output, and output the received sensor output. A indicator 8 is a circuit portion for capturing the received sensor output and indicating the received sensor output itself or the corresponding value of condition (for example, temperature value, humidity value or pressure value) converted from this received sensor output.
Although the example described above is a telemetering system using radio wave for the transmission from the transmitter to the receiver, telemetering systems using ultrasound or infrared wave instead of radio wave have been conventionally used.
Now, it is desired as a matter of course that such a telemetering system as described above has a linearity or a linear relationship between the sensor output from the sensor 1 and the received sensor output indicated on the indicator 8 (that is, a relation in which when one is doubled, the other is also doubled, and when one is tripled, the other is also tripled).
Further, the receiver is placed on the side of measurement-persons so as to receive and indicate results of measurement from the transmitter, so that one receiver can be used for many times telemetering. Therefore, as compared to the transmitter (which is often thrown away after use for only one telemetering as the radiosonde described above), the receiver is generally of higher accuracy with higher-quality parts. Thus, operations in any circuit portion of the receiver generally cause no loss of the linearity between both outputs described above. Further, concerning the transmitter, since the A/D converter 3 and the following circuits (the A/D converter 3, transmission circuit 4, transmitting antenna 5) all deal with digital signals, operations in these circuits basically do not cause any loss of the linearity between both outputs described above.
As a result, from the two reasons described above, the assurances of the linearity of the telemetering system depend on whether the amplifier 2 of the transmitter is of high accuracy with high-quality parts (that is, whether the input and output thereof has a linear relationship between them over a wide rang). For this purpose, the amplifier 2 of the transmitter in a telemetering system required to measure with high accuracy is usually of higher accuracy with higher-quality parts, and thus it is so much expensive.
However, it is useless to construct the amplifier 2 described above with high-quality parts, because the amplifiers included in the transmitters are often thrown away without being recovered after use for onetime telemetering.
The present invention has been made in view of the circumstances described above. It is an object of the invention to provide a telemetering system that keeps a linear relationship between a sensor output of the result of detection by a sensor and a received sensor output indicated at the receiver even if an amplifier included in a transmitter is composed of relatively low-quality and inexpensive parts.
The first invention provides a telemetering system that has a transmitter comprising a sensor and transmitting a transmission wave (ultrasound, infrared wave, radio-wave, etc) modulated with an output signal corresponding to a sensor output from the sensor, and a receiver for receiving the transmission wave from the transmitter and processing the transmission wave, such as demodulating, to generate and indicate a received sensor output corresponding to the sensor output, and the receiver in the telemetering system is configured as follows.
That is, the receiver comprises a correction circuit that has a correction table for storing each value of the received sensor outputs in association with the sensor output corresponding to it, and corrects the received sensor outputs such that they may be linear with respect to the sensor outputs on the basis of the correction table, and outputs the corrected received-sensor-output as an object of the indication.
The configuration described above provides a telemetering system that keeps a linear relationship between a sensor output of the result of detection by a sensor and a received sensor output indicated at the receiver even if an amplifier included in a transmitter is composed of relatively low-quality and inexpensive parts.
The second invention provides a telemetering system that has a transmitter comprising a sensor and transmitting a transmission wave (ultrasound, infrared wave, radio-wave, etc.) modulated with an output signal corresponding to a sensor output from the sensor, and a receiver for receiving the transmission wave from the transmitter and processing the transmission wave, such as demodulating, to generate and indicate a received sensor output corresponding to the sensor out, and the telemetering system is configured as follows.
That is, the transmitter has,
an amplifier for amplifying the sensor output,
an A/D converter for digitizing an output of the amplifier,
a self-ID code storage circuit for fixedly storing an ID code given to each of the transmitters,
a transmission signal generator for combining a digital signal from the A/D converter with an ID code read from the self-ID-code storage circuit in the manner of time division to generate a transmission signal, and outputting the transmission signal, and
a transmission circuit for processing the transmission signal from the transmission signal generator in various ways as required to generate a transmission signal wave, and sending the transmission signal wave as a transmission wave through a transmission wave generator (for example, ultrasonic generator, infrared generator, transmitting antenna, etc.) into the air, and on the other hand the receiver has,
an electrical signal generating device (for example, ultrasonic detector, infrared detector, receiving antenna, etc.) for receiving the transmission wave from the transmission wave generator in the transmitter to generate an electrical signal corresponding to the transmission wave,
a signal processor circuit for processing the electrical signal from the electrical signal generating device, such as amplifying and demodulating, to generate a received signal corresponding to the transmission signal generated by the transmission signal generator in the transmitter, and outputting the received signal, and
a correction circuit which stores a correction table for associating each value of the received sensor outputs with the sensor output corresponding to it (or a difference between both outputs) in advance for each of a plurality of the transmitters, the correction table being related to the ID code of the corresponding transmitter of the plurality of the transmitters, and when the received signal is input from the signal processor circuit, first reads the ID code from the portion associated with the ID code of the received signal and reads the received sensor output from the portion of the received signal other than the portion associated with the ID code, and further corrects the received sensor output such that it may be linear with respect to the sensor output on the basis of the correction table stored in relation to the read ID-code, and outputs the corrected received-sensor-output as an object of the indication.
The configuration described above provides a telemetering system that keeps a linear relationship between a sensor output of the result of detection by a sensor and a received sensor output indicated at the receiver even if an amplifier included in a transmitter is composed of relatively low-quality and inexpensive parts.
The third invention adds the following components to the correction circuit of the receiver in the telemetering system according to the second invention.
That is, the correction circuit further comprises,
a reference voltage input portion for receiving a variable reference voltage, and
correction table creating means which, when a variable reference voltage is applied to the reference voltage input portion, every time the reference voltage changes, reads the ID code from the portion associated with the ID code of a signal from the signal processor circuit and reads the received output from the portion of the signal other than the portion associated with the ID code, and stores the received output in association with the reference voltage (or a difference between them) at the time, these operations being repeated for each change of the reference voltage to create a correction table for associating each value of the received outputs with a value of the reference voltage (or a difference between them) corresponding to it, and further stores the correction table in relation to the read ID-code.
The configuration described above provides a telemetering system that keeps a linear relationship between a sensor output of the result of detection by a sensor and a received sensor output indicated at the receiver even if an amplifier included in a transmitter is composed of relatively low-quality and inexpensive parts. In addition to this, the work for creating the essential correction table of the telemetering system can be made easier by the above configuration.
The fourth invention provides a method for creating a correction table, in which the correction table creating means described above is used in the correction circuit in the receiver in the telemetering system according to the third invention to create the correction table as follows.
That is, the correction table is created through the three steps of,
the first step of disconnecting the sensor from the transmitter,
the second step of connecting a variable reference-voltage generator to the sensor connecting terminal of the transmitter and to the reference voltage input portion of the receiver such that an identical value of the reference voltage may be always applied to them, and
the third step of controlling the variable reference-voltage generator to change the generated reference voltage within the range of variations in the sensor output.
The above described method allows accurate and easy creation of the correction table by using the correction table creating means in the correction circuit in the receiver used in the telemetering system according to the third invention.
The fifth invention adds the following components to the telemetering system according to the third invention.
That is, the transmitter includes a single circuit unit in which the amplifier, the A/D converter, the self-ID code storage circuit and the transmission signal generator are integrated, the circuit unit being removable from other circuit portions, and the input end of the correction circuit in the receiver is adapted to receive a signal from the transmission signal generator included in the circuit unit instead of the received signal from the signal processor circuit.
The configuration described above provides a telemetering system that keeps a linear relationship between a sensor output of the result of detection by a sensor and a received sensor output indicated at the receiver even if an amplifier included in a transmitter is composed of relatively low-quality and inexpensive parts. In addition to this, the work for creating the essential correction table of the telemetering system can be made further easier.
The sixth invention provides a method for creating the correction table, in which the correction table creating means described above is used in the correction circuit of the receiver in the telemetering system according to the fifth invention to create the correction table as follows.
That is, the correction table is created through the four steps of,
the first step of removing the circuit unit from the transmitter,
the second step of inputting a signal from the transmission signal generator of the circuit unit, instead of the received signal, to the correction circuit in the receiver,
the third step of connecting the variable reference-voltage generator to the input end of the amplifier of the circuit unit and to the reference voltage input portion of the correction circuit such that an identical value of the reference voltage may be always applied to them, and
the fourth step of controlling the variable reference-voltage generator to change the generated reference-voltage within the range of variations in the sensor output.
The method described above allows the accurate and easy work for creating the correction table by using the correction table creating means of the correction circuit in the receiver in the telemetering system in accordance with the fifth invention.